The present invention relates to a roof support for a mine gallery which extends at a relatively large angle inclined to the horizontal and comprising three adjacent mine roof support units, of which the upper and the lower roof support units are connected by guiding devices with integrated advancing cylinders located between the sole engaging skids thereof to an elongated abutment beam for pivoting movement about vertical pivot axes, whereas the middle roof supporting unit is connected to the beam tiltable about a pivot axis extending transverse to the elongation of the skids, and in which at least the middle and the lower roof supporting units are connected to each other by a directing cylinder and piston unit.
Such a mine roof support is for instance disclosed in the German Auslegeschrift No. 23 37 218. In this known construction each of the three roof support units comprises a pair of transversely spaced sole engaging skids which are relatively movably connected to each other by bridging members arranged in the region of the skids directed toward the face of the mine gallery to be mined, in which the bridging members are connected to the skids tiltable about tilting axes extending parallel to the skids. Advancing cylinder and piston units are arranged between the skids and the rear ends of these cylinder and piston units are linked to guiding devices arranged between the skids.
The guiding devices of the upper and the lower roof support units are provided at the end thereof directed towards the mine face with linking heads by means of which they are linked to the abutment beam which is arranged above the end sections of the skids which are directed toward the mine face. The pivot axes between the guide means and the abutment beam extend normal to the longitudinal direction of the beam.
The middle roof support unit is directly linked to the abutment beam by means of rods arranged laterally of the skids thereof and the opposite ends of these rods are respectively connected to the beam and the respective skid tiltable about tilting axes extending parallel to the longitudinal direction of the beam. The guide means of the middle roof supporting unit is not linked to the abutment beam, but its free end is provided with a push rod which is pressed against a conveyor.
In addition, a directing cylinder and piston unit is connected at opposite ends to adjacent skids of the middle and the lower roof supporting unit.
One disadvantage of this known construction in which the abutment beam is arranged above the ends of the skids is that the space between the beam and the roof shield of the mine roof supporting units through which a miner may pass is considerably reduced so that this known construction may not be used for mining of coal seams of small height.
A further disadvantage of this known construction is the arrangement of the directing cylinder between adjacent skids of the middle and lower mine roof support units. This arrangement results in that the control of the directing cylinder has to consider the relative movements between the lower and the middle roof support unit during the advance thereof as well as those movements which are produced during the unavoidable deflection of the units during their movement. This means a complicated construction of such a control arrangement. In order for such a control arrangement to work properly, it is adjusted in such a manner that the directing cylinder during advancing movement of one of the two roof supporting units will be made pressureless. That means, that during the advancing movement no directing of the respective unit can be provided. Such directing must be performed while the roof shield and the skids are respectively pressed against the roof and the sole of the mine gallery. This means to overcome exceedingly high friction and therefore the directing cylinder and piston unit has to be constructed of such size so as to overcome this friction.
No directing cylinder and piston units are provided in the construction of the prior art between the skids of the middle and the upper roof support unit. In this known construction the normal position of the upper roof support unit with respect to the abutment beam is to be accomplished only by a slip-in device arranged beneath the abutment beam. In this case it is however to be expected that, due to the given lever ratios, the draw-in of the free ends of the skids between the members of the slip-in device will require a considerable force and therefore a large enough advancing piston and cylinder unit of the guide means.